1. Field of the Invention
The present invention relates to filament winding methods and apparatuses for winding fiber bundles onto the surface of a rotating mandrel, thereby manufacturing a pressure tank or suchlike.
2. Description of the Background Art
The filament winding apparatus is an apparatus for manufacturing hollow containers, such as pressure tanks, pipes, and the like. The filament winding apparatus winds fiber bundles onto a mandrel (a liner) to manufacture a product (a pressure tank or suchlike). The fiber bundle is made up of a fiber material consisting of, for example, a glass fiber and synthetic resin.
In general, the filament winding apparatus manufactures a product by winding fiber bundles by means of both hoop winding ((a) of FIG. 3) and helical winding ((b) and (c) of FIG. 3), thereby making a plurality of layers (e.g., ten layers of more) of fiber bundles (see Japanese Laid-Open Patent Publication No. 10-119138). During the hoop winding, the fiber bundles are wound roughly perpendicular to the axial direction of the mandrel, whereas during the helical winding, the fiber bundles are wound at a predetermined angle with respect to the axial direction of the mandrel. Typically, the filament winding apparatus sequentially winds a small number of fiber bundles (e.g., ten bundles or less) onto the rotating mandrel to cover the mandrel surface with the fiber bundles.
Incidentally, in some cases, for example, to enhance product strength, the helical winding is carried out to form a plurality of layers in a plurality of patterns at different angles with respect to the axial direction of the mandrel. Conventionally, the filament winding apparatus winds a small number of fiber bundles onto the mandrel, and therefore when carrying out the helical winding in a plurality of patterns, product manufacturing takes a significant amount of time. Although the manufacturing time can be shortened by winding wider fiber bundles onto the mandrel, the wider fiber bundles slip on a mirrored portion of the mandrel, resulting in a product of inferior quality. Therefore, filament winding apparatuses that wind a layer of fiber bundles at one time during the helical winding have been proposed (see Japanese Laid-Open Patent Publication Nos. 2002-283467 and 2004-314550). Such filament winding apparatuses are capable of winding a layer of fiber bundles with a single winding operation, but they have difficulty in forming helical winding layers, such that fiber bundles in each layer are uniformly arranged in such a manner as to leave no space therebetween.